1. Field of the Invention
The present invention relates, in general, to a dual-cooled nuclear fuel rod having annular plugs and method of manufacturing the same and, more particularly, to a dual-cooled nuclear fuel rod required to increase output of a standard pressurized light water atomic power plant on a large scale, and a method of manufacturing the dual-cooled nuclear fuel rod, capable of having direct application of welding of the dual-cooled nuclear fuel rod.
2. Description of the Related Art
Just as a fossil fuel such as oil or coal is needed to operate a thermoelectric power plant, nuclear fuel is needed to operate an atomic power plant. Here, as the requisite nuclear fuel, a nuclear fissile material is used. First, the nuclear fissile material is formed into a ceramic pellet called a sintered compact, and the pellet is inserted into a metal tube. Then, the metal tube is sealed with end plugs. Thereby, a nuclear fuel rod is completed. A set of nuclear fuel rods made in this way is fixed to a metal structure. This is called a nuclear fuel assembly. The pellet in the nuclear fuel rod causes a nuclear fission chain reaction to generate heat. This generated heat is transmitted to a coolant, and then is used as energy.
A conventional nuclear fuel rod has a cylindrical shape in which the pellet is charged in a hollow cylindrical cladding tube. Thus, when the heat is generated through the nuclear fission chain reaction, the heat generated adjacent to an outer circumference of the pellet placed into contact with the coolant is easily transmitted to the coolant, whereas the heat generated from the center of the pellet fails to be transmitted to the coolant. In this manner, the cylindrical nuclear fuel rod has low thermal conductivity.
Further, in a dual-cooled nuclear fuel rod composed of two cladding tubes having different diameters and end plugs, when the end plugs are welded to the cladding tubes in order to seal the pellet, a welding torch fails to approach a hollow part of the cladding tube having a small diameter, and thus the welding is difficult. Thus, the dual-cooled nuclear fuel rod is considerably restricted by the inner diameter of the cladding tube which the welding torch cannot approach.